This invention relates to apparatus used in completing or treating earth wells and particularly to continuous orifice fill devices.
As casing is lowered into an earth well, a shoe at the lower end of the casing is usually provided which has an orifice device coupled across its open end. The orifice device restricts the amount of upward flow of material through the casing as the casing is lowered into the well bore, thus allowing the casing to partially "float" its way down the well bore.
In addition, such devices usually have a valve which may be actuated to prevent back flow of material up the casing once the casing is "set" in position in the well bore.
Often, the upward flow preventing valve of the device is actuated by plugging the orifice of the device and then applying pressure from above to break shear pins holding the inner orifice part in place to release the valve as the inner orifice part is removed.
It has been found that the valves of such devices often do not fully seal off back flow into the casing. The use of two or more orifice devices along the casing would provide better sealing, but the "break away" part of the upper device would interfere with the actuating of the valves of the lower device(s).